Refactor examples

[paulf81]

Refactor examples for v4

This pull request refactors the examples around the v4 structures and style and in general cleans up the examples folder, which had become a sort of unsorted list of examples. Specifically,

• Examples are now organized into top level over-arching examples in the root examples folders, and then examples grouped by topic in subfolders
• The top level examples are completely redone to incrementally introduce FLORIS, in a way consistent with v4
• Each example now includes a self-describing docstring at the top of each
• Every example is refactored for v4 code and style, as well as overall improvements, style, spelling, ruff, etc

In addition to these changes, some supporting changes were made to the code

• Spelling errors of the word heterogeneous are fixed throughout the code
• A bug in 'mixed' operation model (which masked yaw_angles > 0, when it should've been != ) is fixed, which was identified in making one of the examples
• several additional properties were added to FlorisModel, adding to layout_x and layout_y, these are wind_directions, wind_speeds, turbulence_intensities, n_findex and n_turbines. This change makes the examples more readable without the core.flowfield intermediates
• A bug in ParallelFlorisModel is fixed (sum -> nansum, fixed concatenating parallel results)

Finally, changes to CI include:

• CI running of examples update to include checking examples in subfolders

@misi9170 and @rafmudaf and @ejsimley I think this is now ready to review. We talked about automatically generating html versions of the examples and so far this is proving difficult, so maybe that could still be done, but as part of another pull request

[misi9170]

Aren't examples 002--004 here covered by the 002_visualizations.py example in the main examples/ directory?

[paulf81]

Technically, yes, there a little more blocked out, but it's true not strictly necessary, but maybe convenient to have such a single-purpose example? Also up for discussion...

[misi9170]

Hi @paulf81 , I have made a bunch of minor comments, but overall this looks good.

I think the changes outside of the examples (heterogeneous, bugfixes to ParallelFlorisModel, MixedOperationTurbine bugfix).

On the @propertys available on FlorisModel, do we need to check that these are matched on UncertainFlorisModel (I see that you've already updated ParallelFlorisModel)?